The invention relates generally to monitoring fluid flow, and more particularly, to detecting fluid line conditions upstream of the monitoring position.
Fluid delivery systems having positive pressure pumps for infusing parenteral fluid to a patient have become fairly common. In many cases the pump is a peristaltic type in which a plurality of fingers, rollers, or other devices, sequentially constrict a flexible tube through which the parenteral fluid is supplied. Such fluid delivery systems also include, in addition to the pump, an inverted bottle or bag or other means of supply of parenteral fluid, an intravenous (IV) administration set which is secured to the supply of parenteral fluid and includes the flexible tube, and a cannula which is mounted to the distal end of the tube and which is adapted to be inserted into the patient's blood vessel to thereby infuse the parenteral fluid.
One common problem facing infusion systems is the evaluation of the condition of the fluid supply system upstream of the pump. Where an occlusion of the tube exists upstream of the pump, the pump will not succeed in infusing the parenteral fluid to the patient even though the pump may continue to operate. Where the parenteral fluid supply becomes depleted, once again the pump may continue to operate but no parenteral fluid will be delivered to the patient.
A prior method for detecting depletion of the fluid supply or an upstream occlusion was visual observation. A drip chamber may be inserted in the fluid line at a position downstream from the fluid supply for monitoring the rate and quantity of fluid administered. However, visually verifying the existence of drops requires the time of an attendant which can be an undesirable burden on the hospital staff. Opto-electric drop detectors may be utilized in conjunction with the drip chamber. These detectors are capable of automatically detecting upstream occlusions due to a clamp or kink in the upstream tubing and an empty IV fluid supply container by detecting an absence of drops. An upstream occlusion can also be detected by the addition of a pressure sensor to the fluid line upstream of the pump. However, the use of these devices can add a considerable additional expense. Additionally, movement of the administration set, if severe enough, can cause extra drops to fall from the drop former or can interrupt the drops causing false counts and false alarms. Ambient light can also interfere with an optical drop sensor and render it inaccurate.
In some cases it would be useful to automatically provide information relating to the pressure of the supply fluid or the "head" pressure. From the head pressure, an upstream occlusion can be detected as well as an empty fluid supply.
Pump systems have been disclosed which include a downstream pressure sensor used for detecting improper fluid communication with the patient. Such systems include U.S. Pat. No. 4,743,228 to Butterfield; U.S. Pat. No. 4,460,355 to Layman; U.S. Pat. No. 4,534,756 to Nelson; and U.S. Pat. No. 4,846,792 to Bobo, Jr. et al. Where such systems use a pump or other fluid pressure control means which communicates the head pressure to the outlet side of the pump, it would be of value to utilize the existing downstream pressure sensor to determine upstream fluid conditions. This would result in less expense both in the pump and in the administration sets.
Hence, those skilled in the art have recognized the need for a fluid line monitoring system which can automatically detect upstream fluid line occlusions as well as measure the head pressure. Additionally, those skilled in the art have recognized a need to reduce the cost of determining such upstream fluid line conditions. The present invention fulfills these needs.